Defrosting means for refrigeration apparatus



Jan. 18, 1949. G. S. MccLoY 2,459,173

DBFROSTING MEANS FOR REFRIGERATION APPARATUS Filed Feb. 5, 1946 2 Sheets-Sheet 1 L'vAPoRAToR WITNESSES: m INVENTOR GRAHAM SHMQ CLOY Patented Jan-18.1949

Graham 8. McCloy, Springfield, Mama, to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corp ration of Pennsylvania Application February 5, 1946, Serial No. 645,612

This invention relates to refrigerating apparatus and more especially'to a means forrapidly defrosting such apparatus.

It is an object of this invention to Provide a.

novel refrigerating circuit adapted to defrost the evaporator when desired.

It is a further object ofthe invention to provide novel means for increasing the active quantity of refrigerant flowing in a refrigerating. appara- These and other objects are effected by. the

. invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which: I

Fig. 1 is a schematic drawing of refrigerating apparatus and of the defrosting apparatus of this invention;

Fig. 2 is a schematic drawing of a modification of the defrosting apparatus of Fig. 1;

Fig. 3 is a schematic drawing of refrigerating apparatus and of a modification of the defrostin apparatus of this invention; and

Fig. 4 is a schematic drawing of the thermostatic expansion valve of Fig. 3.

Referring now to the drawings for a detailed explanation, the reference numeral In designates a compressor driven by an electric motor II which receives electrical energy through leads l2 and I3 and is controlled by a switch ll actuated thermostatically. The refrigerant vapor of the apparatus, when compressed by the compressor 10, flows through the pressure conduit it to the condenser l5 wherein it is liquefied and then passes through a capillary tube I6 and through a slightly larger tube l8 into a vessel 20. The refrigerant liquid thereupon flows through a con- The vaporized refrigerant thereupon flows to a header 28 and then through a suction tube 30 to the compressor Ill. The latter portion 33 of the suction tube 36 is in heat transfer relationship with the pressure conduit 14, and an intermediate portion of the suction tube 36 is in heat transfer relationship with the capillary tube l6.

The switch i1 is actuated by a metal bellows 35 responsive to the vapor pressure of a volatile fluid in a bulb 3i located on the evaporator 26. The switch l1 and its actuating mechanism starts and stops the compressor periodically to maintain the temperature of the evaporator 26 substantially constant during normal operation.

An electric heater .38 is arranged to heat the v recla m. (01.62-3) tube II. The heater a 2 may be energized through leads I! from the leads i2 and is controlled by an electric switch 42 located in one of the leads II. The switch 62 is open during normal operation of the apparatus and is closed only when the evaporator 26 is to be defrosted. The vessel 28 is preferably enclosed in heat insulating material so that substantially no evaporation of the refrigerant liquid therein takes place.

An inverted U tube 36 connects through one leg 31 with the lower portion of the vessel 26 and through the other leg with the conduit 24. The inverted U tube 36 comprises a portion 44 which is elevated above the small conduit 22, and the height of this elevation is so proportioned with respect to the resistance of the small conduit 22 to the flow of refrigerant therethrough during normal operation of the apparatus, that the refrigerant will flow through the small conduit 22 in preference to the elevated portion 64 of the U tube 36. During such operation, the refrigerant liquid will rise in the leg 31 of the U tube 36 to such a height 39 that its static head counterbaiances the pressure drop in the refrigerant across the small conduit 22. Fig. 1 shows the apparatus in its normal operating position.

To effect defrosting of the evaporator 26, the switch 62 is closed to energize the heater 38 simultaneously with the motor II. The heat supplied by the heater 38 vaporizes such a quantity of the refrigerant liquid flowing through the tube 18, that the small conduit 22 is incapable of passing the refrigerant at a pressure drop across the conduit 22 which is less than the static head of the liquid refrigerant adapted to be contained in the leg 31 of the inverted U tube 36. As a result, the refrigerant will flow out of the vessel 20 through the U tube 36, and since this tube con nects with the bottom of the vessel 26, the liquid refrigerant therein will be forced out. The liquid refrigerant thus forced out of vessel 20 fills the header 28 and flows into the portion 33 of the conduit 86.

The hot refrigerant vapor in conduit M vaporizes the refrigerant liquid in the portion 33 of the conduit 30 and thereby raises the suction pressure in theconduit 30 and in the evaporator 28 so that the temperature of the liquid refrigerant in the evaporator 28 rises above the freezing point of water. Switch II will remain closed because of the increased temperature of the evaporator, and the compressor l 0 will continue'to circulate relatively warm liquid refrigerant through Moon-2a ant liquid flowing through the evaporator, but its heat is not essential in defrosting the evaporator 26.

The elements comprising the vessel 20, the U tube 36, the conduit 22, and the heater 38 form an apparatus for addingliquid refrigerant to the quantity normally circulating -in-the refrigerating circuit. Since this liquid refrigerant adding apparatus contains no moving parts, it will be relatively free from mechanical failures. This apparatus, however, may be replaced by any other apparatus for adding liquid refrigerant to the circulating system, such, forexample, as shown in Patents Nos. 2,133,948 and 2,133,961 to Buchanan.

A modification of the apparatus is shown in Fig. 2. In this modification; a heater 46, similar to heater 38, is directly applied to the vessel 20 of Fig. 1.

In the embodiment of the invention shown in Figs. 3 and 4, the elements which are identical with the elements shown in Fig. 1 are provided withthe same reference numerals. In this em-- bodiment, the reference numeral 50 designates a liquid receiver whichreceives refrigerant liquid from the condenser I5 and stores a portion of it during the normalv operation of the apparatus. The liquid refrigerant flows from the liquid receiver through a liquid line 52 to a thermostatic expansion valve 54, which is of well-known design, being such, for example, as'the thermostatic expansion valve shown in Patent. No. 1,971,695 to Ploeger. The thermostatic expansion valve 54 connects with the conduit 24.

The essential working elements of the thermostatic expansion valve 54 are shown schematically in Fig. 4 and comprise a valve 56 which controls the flow. of liquid refrigerant to the evaporator 26. The valve 56 is actuated by a metal bellows 58 which connects through a tube 60 with a temperature-responsive bulb 62 and which may connect with a second bulb 64 of the same character.

The bulb 62 is in heat exchange relationship with the refrigerant issuing from the evaporator 26 and the bulb 64 with the refrigerant entering the compressor Ill. The bellows 58, tube 60, and the bulbs 62 and 64 contain a volatile refrigerant which is mainly in the vapor phase, so that the pressure in the bellows corresponds to the tem-- is not energized. The bulb 62 will be the coldest part of the control system of the bellows 58 and will actuate the bellows 58 in cooperation with the suction pressure of the evaporatorv 26 to maintain a substantially constant superheat in: the refrigerant vapor issuing from the evaporator 26,

as is well understood in the art. I v

When it is desired to defrost the evaporator 26, switch 42 is closed and the heater. 66 is energized simultaneously with. the motor I I. The

heater 66 warms the control bulb 62 and causes the volatile liquid therein to vaporize so that the valve 56 is opened wide by the bellows 56. When the control valve 66' is opened wide, the refrigerant liquid stored in the liquid receiver 60 will be forced into the evaporator and into t e If itis desired to secure'a inorerapid defrost-' ing'of the evaporator -26,"a -secorid heater 10 may be placed in heat exchange relationship with the conduit 24 or with any portion of the evaporator 26. The heater 16 may be energized through leads 12.,and leads '46, and will then be energized simultaneously with the heater 66.

The function of the bulb 64 is to prevent liquid refrigerant from vjentering the compressor Hi. When thecoutrolbulb 62 is warmed to a higher temperature than the bulb 64, the volatile liquid .will migrate to bulb 64 so that the temperature of the latter controls the pressure in the metal bel- If liquid refrigerant reaches a point in the conduit 36 adjacentthe bulb 54 the partial 'vaporization of this liquid will'cool the bulb 64 lows 58.

and the volatile liquid th r in; This decreases the pressurewithin thebellows 56 and results'in apartialclosin'g'of the valve 56. "When the valve 56 is'thus partially closed, less of the liquid refrigerant will enterthe suction conduit 36.; This liquid will be completely vaporized so that none of it will enter the compressor in the liquid state.

The use of the bulb 64 is thus merelya protection for the compressor and its use is not essential.

It will be apparent from the above description that this invention provides several means" of defrosting an evaporator, each of which :adds liquid refrigerant to the active quantity of refrigerant liquid circulating in a refrigerating apparatus in which the suction tube and the pressure conduit near the compressor are in heat'tr'ansfer relationship. It will be further apparent that a means has been provided for increasingthe active quantity of refrigerant flowing in a refrigerating apparatus, which means is devoid of moving parts.

While the invention has been shown in several forms, it will be obviousto those skilled in the art that it is not so limited, but is susceptible of various other changes and modificationswithout departing from the spiritthereof.

What is claimed is: s

1. In refrigerating apparatus, the combination of a compressor, a condenser, a vesseladapted for accumulating and holding refrigerant liquid in an inactive state during the normal operation of said apparatus, an evaporator, a first conduit connecting said compressor with said condenser, a second conduit connecting said condenser with said vessel, a third conduitconnecting said vessel with said evaporator, a fourth conduit connecting said evaporator with said compressor, atleasta portion of said fourth conduit being inheat-exchange relationship with the refrigerant, vapor compressed by said compressor, said". apparatus being arranged to produce refrigeration W of said evaporator and heatdissipatio I I of said condenser during'normal operation,,-a'nd actuating means. for producing abnormal operation of said apparatus to defrost said evaporator, said means being adapted to discharge the refrigerant liouid from said vessel through said third conduit, said vessel, when being discharged supplying sufllcient refrigerant liquid to flood both said evaporator. and said portion of the fourth conduit. v

2. In refrigerating apparatus, the combination of a compressor, a condenser, a vessel adapted for accumulating and holding refrigerant liquid in an inactive state during the normal operation of said apparatus, an evaporator, a first conduit connecting said compressor with said condenser, a second conduit connecting said condenser with said vessel, a third conduit connecting said vessel with said evaporator, a fourth conduit connecting said evaporator with said compressor, portions of said first and fourth conduits being in heat exchange relationship, said apparatus being arranged to produce refrigeration by means of said evaporator and heat dissipation by means of said condenser during normal operation, and actuating means for producing abnormal operation of said apparatus, said means being adapted to dis-' charge the refrigerant liquid from said vessel through said third conduit, said vessel when beingdischarged supplying sufiicient refrigerant liquid to fiood both said evaporator and said portion of the fourth conduit.

3. In refrigerating apparatus, the combination of a compressor, a condenser, a vessel adapted for accumulating and holding refrigerant liquid in an inactive state during the normal operation of said apparatus, an evaporator, a first conduit connecting said compressor with said condenser, a second conduit connecting said condenser with said vessel, a third conduit connecting said vessel with said evaporator, a fourth conduit connecting said evaporator with said compressor, portions of said first and fourth conduits being in heat exchange relationship, said apparatus being arranged to produce refrigeration by means of said evaporator and heat dissipation by means of said condenser during normal operation, and actuating means for producing abnormal operation of said apparatus, said means being adapted to heat and discharge the refrigerant liquid from said vessel through said third conduit, said vessel when being discharged supplying sufficient refrigerant liquid to fiood both said evaporator and said portion of the fourth conduit.

4. In a mechanical refrigerating circuit comprising an evaporator, a compressor, a condenser, and a flow-impeding device, the combination with said circuit of a vessel connected between said flow-impeding device and said evaporator to trap refrigerant liquid in said vessel, the connection between said vessel and said evaporator comprising a first outlet conduit connected at one end with a lower portion of said vessel and extending above the liquid in said vessel, said first conduitcommunicating at its other end with said evaporator, and a second outlet conduit connected at one of its ends with an upper portion of said and a flow-impeding device, the combination with I said circuit of a vessel connected between said flow-impeding device and said evaporator to trap refrigerant liquid in said vessel, the connection between said vessel and said evaporator comprising a first outlet conduit connected at one end with a lower portion of said vessel and extending upwardly and communicating at its other end with said evaporator, and a second outlet conduit connected at one of its ends with an upper 6 Y portion of said vessel and communicating at its other end with said evaporator, said second conduit having a constricted passage to so impede the refrigerant flowing therethrough, that during normal operation of said circuit, the refrigerant liquid rises in, but does not flow through said first conduit, and actuating means for so increasing the refrigerant vapor in said vessel when said compressor is operating that refrigerant flows through said first conduit.

6. In a mechanical refrigerating circuit com-- prising an evaporator, a compressor, a condenser, and a flow-impeding device, the combination with liquid said circuit of a vessel connected between saidfiow-impeding device and said evaporator to trap refrigerant liquid in said vessel, the connection between said vessel and said evaporator comprising a first outlet conduit connected at one end with a lower portion of said vessel and communicating at its other end with said evaporator, said first conduit having an elevated portion to form a-siphon in said conduit, and a second outlet conduit connected at one of its ends with an upper portion of said vessel and communicating at its other end with said evaporator, said second conduit having a constricted passage to so impede the refrigerant flowing therethrough, that during normal operation'of said circuit, the refrigerant liquid rises in, but does not fiow through said first conduit, and actuating means for so increasing the refrigerant vapor in said vessel when said compressor is operating that refrigerant liquid flows through said elevated portion of said first conduit to actuate said siphon.

'7. In a mechanical refrigerating circuit comprising an evaporator, a compressor, a condenser,

and a flow-impeding device, the combination with said circuit of a vessel connected between said flow-impeding device and said evaporator to trap refrigerant liquid in said vessel, the connection between said vessel-and said evaporator comprising a first outlet conduit connected at one end with a lower portion of said vessel and communicating at its other end with said evaporator, said first conduit having an elevated portion to form a siphon in said conduit, anda second outlet conduit connected at one of its ends with an upper portion of said vessel and communicating at its other end with said evaporator, said second conduit having a constricted passage to so impede the refrigerant flowing therethrough, that during normal operation of said circuit the refrigerant liquidrises in, but does not fiow through said first conduit, and means for heating the refrigerant liquid after its pas age through said fiow impeding device and prior to its passage through said constricted passage to increase the refrigerant vapor in said constricted passage when said compressor is operating so that refrigerant liquid fiowsthrough said elevated portion of said first conduit to actuate said siphon.

8. A refrigerating system comprising a plurality of refrigerant passages connected in, a circuit, pumping means in said circuit for circulating a volatile refrigerant therethrough at a substantially constant rate, and means for varying the effective quantity of refrigerant liquid circulating in said circuit, said means comprising a vessel connected in said circuit through an inlet and an outlet, said vessel having a portion located below said outlet to trap refrigerant liquid insaid portion and hold said liquid in an inactive state, a restriction in said circuit between said outlet and said pumping means, a tube connected' at one end with said trapping portion of striction and the elevationof said portion ofthe tube being so arranged that the normal proportion of refrigerant vapor and liquid flowing through said restriction is insumcient to cause refrigerant liquid to flow through said tube, and actuating means adapted to so increase the ratio of refrigerant vapor to refrigerant liquid flowing through said restriction that the resistance of said restriction to 'said'flow causes refrigerant liquid to flow from said vessel portion through said tube, said actuating means being adapte to be rendered active and inactive,

9. A refrigerating system comprising a plurality of refrigerant passages connected in a circuit, pumping means in said circuit for circulating a volatile refrigerant therethrough at a substantially constant rate, a flow impeding device in saidy'circuit, said flow impeding device and pumping means dividing said circuit into a low pressure and a highpressure side and means for varying the effective quantity of refrigerant liquid circulating in said circuit, said means comprising a vessel connected in the low pressure side of said circuit through an inlet and an out- I let, said vessel having a portion located below said outlet to trap refrigerant liquid in said portion and hold said liquid in an inactive state, a restriction in said circuit between said outlet and said pumping means, a. tube connected at one end with said trapping portion of said vessel and at its other end with said low pressure side of said circuit at a point beyond said restriction, said tube having a portion elevated above the outlet of said vessel, said restriction and the elevation of said portion of the tube being so arranged that the normal proportion of refrigerant vapor and liquid flowing through said restriction i insuflicient to cause refrigerant liquid to flow through said tube, and actuating means adapted to so increase the ratio of refrigerant vapor to refrigerant liquid flowing through said restriction that the resistance of saidvrestriction to said flow causes refrigerant liquid to flow from said vessel portion through said tube, said actuating means being adapted to be rendered active and inactive. g

10. In refrigerating apparatus, the combination of a compressor, a condenser for receiving compressed refrigerant vapor from said compressor, a liquid receiver communicating with said condenser, an expansion valve communicating with said liquid receiver, an evaporator communieating with said expansion valve, a conduit connecting said evaporator with said compressor, said conduit being in heat exchange relationship with the compressed vapor issuing from said compressor, said apparatus being arranged to produce refrigeration by means of said evaporator and heat dissipationby means of said condenser during normal operation, said liquid receiver storing such a quantity of refrigerant liquid during normal operation of the apparatus that when said valve is opened wide both said evaporator and said conduit are supplied with rewhereby the refrigerating action of said evapora f 'tor "is reducedv so that frost whichv may'fl hav'ei' formed thereon is, permitted to. melt,

ing abnormal operation of said apparatus, said means being adapted for opening said expansion valve wide to admit refrigerant liquid to said evaporator and conduit, said refrigerant liquid being vaporized in said conduit by the heat of the, refrigerantvapor issuing from the compressor,

11. In refrigerating apparatus, the combina-, tion of a compressor, a condenser, a liquid receiver communicating with said condenser, a. thermostatic expansion 'valve communicating with said liquid receiver, an evaporator communicating with said expansion valve, a iirst. conduit connecting said compressor with said condenser,

a second conduit connecting said evaporator with said compressor, said first and second conduits being, in heat exchange relationship, said expan sion valve having a temperature-responsive bulb adapted to open said valve at a predetermined temperature above that of the evaporator, said bulb lying in heat exchange relationship with the refrigerant vapor flowing from said evaporator and with a heating element, said apparatus being arranged to produce refrigeration by means of said evaporator and heat dissipation by means of said condenser during normal operation, said liquid receiver storing such a quantity of refrigerant liquid during normal operation of the apparatus that when said valveis opened wide both the evaporator and said second c'onduitare supplied with refrigerant liquid, and actuating means for producing abnormal operation of saidapparatus, said means being adapted for energizing said heating element to open said expansion valve wide to admit refrigerant liquid to said evaporator and second conduit, said, refrigerant liquid vaporizing in said second conduit to,

cool the refrigerant vapor in said first conduit, whereby the refrigerating action of said evaporator is reduced so that frost which may have accumulated thereon is permitted to melt.

12. In refrigerating apparatus, the combination of a compressor, acondenser, a liquid receiver communicating with said condenser, a, thermostatic expansion valve, an evaporator, a first conduit connecting said compressorwith said condenser, a second conduit connecting said liquid receiver with said expansion valve, a third conduit connecting said expansion valve with said evaporator, a fourth conduit connecting said element, the second of said bulbs being in heat exchange relationship with the refrigerant entering said compressor, said apparatus being arranged to producerefrigeration by means of said evaporator and heat dissipation by means of said condenser during normal operation, said liquid receiver storing such a quantity ofrefrigerant liquid during normal operation of the apparatus that when said valve is opened wide both the evaporator and said fourth conduit are supplied with refrigerantliquid. and means for producing abnormal operation of said apparatus, said means 7 being adapted for energizing said heating element to opensaid expansion valve wide to admit refrigerant liquid to said evaporator and fourth conduit, said refrigerant liquid vaporizing therein to cool the refrigerant vapor in said firstconduit, whereby the refrigerating action of said evaporator is reduced so that frost which may have accumulated thereon is permitted to melt, thequantity of refrigerant liquid in said two tem- 10 mature-responsive bulbs being limited so that either of said two bulbs can contain said entire REFERENCES CITED quantity, whereby the colder of said two bulbs The following references are of record in the -controls said thermostatic expansion valve, said file hi pa ent: heating element. when energized and with the 5 NIT-ED compressor operating, heating said first bulb to U STATES PATENTS a temperature higher than that of said second Number Name Date bum 2,133,961 Buchanan Oct. 25, 1930 GRAHAM s c1 ,oy ,385,667 Webber Sept. 25, 1945 

